Le comportement en fluage et à la relaxation d’aciers au chrome est étudié par indentation instrumentée, ce qui permet de solliciter le matériau dans des conditions de chargement proches de celles des essais classiques. L’objectif principal n’est pas ici de se substituer à eux mais de proposer un classement des matériaux selon leur sensibilité en fluage / relaxation par indentation.Pour cela, nous déterminons, d’abord à température ambiante, les conditions optimales d’indentation en termes de temps de maintien, de charge de maintien, de vitesse de chargement et de forme de l’indenteur. La méthodologie proposée est appliquée ensuite à plus hautes températures jusqu’à 400 °C (limitation de l’instrument). A température ambiante, le coefficient de sensibilité à la contrainte obtenu correspond à la valeur extrapolée à température ambiante des données obtenues par fluage classique à hautes températures. Malheureusement, cette corrélation n’est pas vérifiée par indentation à chaud probablement à cause de la dérive thermique subie par l’instrument. Le comportement en relaxation par indentation a également été étudié à température ambiante. Nous proposons deux méthodes analytiques permettant de déterminer le coefficient d’homothétie défini dans la théorie de Hart. L’inverse de ce coefficient, déduit de la relaxation par indentation, est comparable au coefficient de sensibilité à la contrainte déterminé par fluage, ce qui permet de comparer les deux modes de sollicitation. Malgré les difficultés expérimentales rencontrées, nous proposons un classement des matériaux selon leur sensibilité au fluage. / The creep and relaxation behaviors of based-chromium steels are studied by instrumented indentation, which allows the application of loading conditions close to those of conventional tests to the material. The main objective here is not to substitute the classical tests by the indentation one, but to give a classification of materials according to their sensitivity in creep/relaxation by indentation.For that, we first determine at room temperature the optimum conditions of indentation in terms of holding time, indentation loading, the unloading and loading rates and indenter shape. The proposed methodology is afterwards applied at higher temperatures below 400 °C due to instrument limitation. At room temperature, we obtained the stress sensitivity exponent that corresponds to the extrapolated value at ambient temperature of data obtained by classical creep tests performed at high temperatures. Unfortunately, this correlation is not obtained by indentation at higher temperatures probably due to thermal drift of the instrument. We have also studied at room temperature the behavior in relaxation by indentation. We propose two analytical methods for determining the coefficient of scale defined in Hart's theory. The interest of this coefficient inferred from the relaxation by indentation is that its inverse is comparable to the stress sensitivity exponent determined by indentation creep, which allows to compare these two modes of solicitation. Despite the experimental difficulties encountered, we propose a classification of the tested materials according to their creep sensitivity.

Background: To describe the scoring methodology and MRI assessments used to evaluate the cross-sectional features observed in cases and controls, to define change over time for different MRI features, and to report the extent of changes over a 24-month period in the Foundation for National Institutes of Health Osteoarthritis Biomarkers Consortium study nested within the larger Osteoarthritis Initiative (OAI) Study. Methods: We conducted a nested case-control study. Cases (n = 406) were knees having both radiographic and pain progression. Controls (n = 194) were knee osteoarthritis subjects who did not meet the case definition. Groups were matched for Kellgren-Lawrence grade and body mass index. MRIs were acquired using 3 T MRI systems and assessed using the semi-quantitative MOAKS system. MRIs were read at baseline and 24 months for cartilage damage, bone marrow lesions (BML), osteophytes, meniscal damage and extrusion, and Hoffa- and effusion-synovitis. We provide the definition and distribution of change in these biomarkers over time. Results: Seventy-three percent of the cases had subregions with BML worsening (vs. 66 % in controls) (p = 0.102). Little change in osteophytes was seen over 24 months. Twenty-eight percent of cases and 10 % of controls had worsening in meniscal scores in at least one subregion (p < 0.001). Seventy-three percent of cases and 53 % of controls had at least one area with worsening in cartilage surface area (p < 0.001). More cases experienced worsening in Hoffa- and effusion synovitis than controls (17 % vs. 6 % (p < 0.001); 41 % vs. 18 % (p < 0.001), respectively). Conclusions: A wide range of MRI-detected structural pathologies was present in the FNIH cohort. More severe changes, especially for BMLs, cartilage and meniscal damage, were detected primarily among the case group suggesting that early changes in multiple structural domains are associated with radiographic worsening and symptomatic progression.

A poetry manuscript.

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Disputats, Linköpings universitet, 2008. / Findes også på internet (PDF-format): http://www.diva-portal.org/diva/getDocument?urn_nbn_se_liu_diva-10489-1__fulltext.pdf. På cd-rom: Supplerende materiale i PDF-format. Med litteraturhenvisninger.

<p> </p><div> <div> <div> <p> </p><div> <div> <div> <p> </p><div> <div> <div> <p>The current state of the art in biopotential recordings rely on radiative electromagnetic (EM) fields. In such transmissions, only a small fraction of this energy is received since the EM fields are widely radiated resulting in lossy inefficient systems. Using the body as a communication medium (similar to a ’wire’) allows for the containment of the energy within the body, yielding order(s) of magnitude lower energy than radiative EM communication. The first part of this work introduces Animal Body Communication for untethered rodent biopotential recording and for the first time this work develops the theory and models for animal body communication circuitry and channel loss. In vivo experimental analysis proves that ABC successfully transmits acquired electrocardiogram (EKG) signals through the body with correlation greater than 99% when compared to traditional wireless communication modalities, with a 50x reduction in power consumption. The second part of this work focusses on the analysis and design of an Electro-Quasistatic Human Body Communication (EQS-HBC) system for simultaneous sensing and transmission of biopotential signals. In this work, detailed analysis on the system level interaction between the sensing and transmitting circuitry is studied and a design to enable simultaneous sensing and transmission is proposed. Experimental analysis was performed to understand the interaction between the Right Leg-Drive circuitry and the HBC transmission along with the effect of the ADC quantization on signal quality. Finally, experimental trials proves that EKG signals can be transmitted through the body with greater than 96% correlation when compared to Bluetooth systems at extremely low powers. </p> </div> </div> </div> </div> </div> </div> </div> </div> </div>

La présente thèse propose d’observer les distinctions des attitudes face à la légitimité de la police et l’emploi de la force chez des futurs policiers québécois à différents stades de leur formation policière initiale en école. Plusieurs chercheurs et de nombreux policiers sont d’avis que le métier de policier est appris dans son intégralité sur le terrain et que, de facto, la formation en Académie de Police est inutile. Or, est-ce vraiment le cas? Se pourrait-il que la formation policière engendre des changements d’attitudes graduels et subtils chez les futurs policiers de sorte que ceux-ci sont imperceptibles, mais à la fois les préparent à l’exercice de la profession policière? C’est précisément ce que la thèse vise à documenter, en lien avec les questions de légitimité de la police et d’emploi de la force. La formation policière sera considérée avoir un apport si les futurs policiers plus avancés dans la formation ont des attitudes plus positives face à la légitimité de la police et sont plus favorables à l’emploi de la force que leurs collègues plus novices. Sans contredit, la littérature sur la légitimité de la police est vaste. Or, ce concept est, dans la grande majorité du temps, abordé de façon unidirectionnelle où les citoyens évaluent la légitimité de la police. Il est ici proposé de changer d’approche et d’adopter plutôt une perspective interactionniste et dialogique de la légitimité de la police où la perception de la légitimité de la police qu’ont les citoyens découle du regard que les policiers portent sur la légitimité de leur institution. Dans ce contexte, la formation policière est vue comme une voie de transmission de la légitimité de la police à laquelle sous-tend un processus de socialisation professionnelle qui permet l’adhésion à la culture policière. Ce sujet de recherche est abordé d’un point de vue macrosociologique grâce à une méthodologie quantitative basée sur une enquête transversale à mesures répétées. Concrètement, l’analyse consiste en des comparaisons de moyennes d’attitudes face à la légitimité de la police et face à l’emploi de la force à différents stades de la formation policière. Pour ce faire, les données ont été collectées, dans un premier temps, auprès de 1 494 futurs policiers en formation au Québec. Dans un deuxième temps, pour écarter l’hypothèse alternative que l’explication des écarts d’attitudes entre plusieurs groupes d’étudiants à différents stades de formation pourrait en fait provenir d’une maturation généralisée à tous les jeunes en phase d’émergence de l’âge adulte (c’est-à-dire, entre 18 et 25 ans), la thèse incorpore une dimension de comparaison avec des citoyens de la même tranche d’âge en considérant un échantillon de 601 étudiants d’autres programmes de formation. Conformément aux trois objectifs spécifiques de la thèse, les résultats ont permis d’observer qu’au cours de la formation policière : 1) les attitudes des futurs policiers plus avancés dans la formation sont plus positives et plus distinctes de celles de leurs homologues d’autres programmes de formation que les attitudes des futurs policiers en début de formation, ce qui indique un apport de la formation policière dans le développement de la légitimité de la police chez ceux en voie d’exercer le métier , 2) les attitudes du groupe de futurs policiers plus avancés dans la formation sont plus homogènes que celles de leurs comparses plus novices, ce qui suggère l’adhésion à la culture policière, et 3) les futurs policiers en fin de formation présentent une dissociation dans leurs attitudes face à la légitimité et face à l’emploi de la force relativement à leurs collègues plus novices, dans le sens où leurs attitudes face à la légitimité de la police sont moins fortement prédictives de leurs attitudes face à l’emploi de la force. Ce dernier résultat semble mettre en lumière le développement d’un jugement critique face à la légitimité de la police et son pouvoir d’emploi de la force au cours de la formation policière. La thèse conclut donc que l’utilité de la formation policière en école est loin d’être vaine; elle paraît occasionner des changements d’attitudes subtils et graduels qui peuvent se révéler importants à l’exercice du métier de policiers. / The thesis suggests studying the variations in attitudes toward police legitimacy and the use of force for in-training police students at distinct phases of police initial training at the Police Academy. Several researchers and many police officers attest that the police craft is solely acquired and learnt on the street and, therefore, the training provided at the Police Academy is pointless. Yet, is this really so? Could it be that the training provided by the Police Academy triggers such gradual attitude changes that they go unnoticed, while contributing to preparing the recruits to perform the police line of work? These questions underlie this thesis, specifically in regard to police legitimacy and use of force in the sense that the contribution of the police training would be unveiled if in-training police students more advanced in the study program have more positive attitudes toward police legitimacy and are more favourable to police use of force. Undeniably, the literature on police legitimacy is extensive. However, authors generally adopt a unidirectional point of view where police legitimacy equates to citizen perceptions of police. Rather, it is advocated here that an interactionist and dialogic approach is better suited to understand police legitimacy. The latter is based on the premise that citizens’ perceptions of police legitimacy ensue from the outlook that patrol officers have on the legitimacy of their institution. In that case, police training is considered a professional socialization process which acts as a police legitimacy transmission channel leading to the conformity to police culture. The thesis tackles this research topic with a macrosociological approach supported by a quantitative methodology based on a repeated cross-sectional research design. Precisely, the analytical strategy consists of mean comparisons of attitudes toward police legitimacy and use of force scores at different stages of the police training curriculum. As a first step, data were gathered from a sample of 1 494 future police officers in training in Quebec, Canada. Then, in order to rule out the alternative hypothesis that attitude score fluctuations between groups at different stages of the training could result from a maturation phenomenon generalized to all youth in the phase of emerging adulthood (i.e. 18-25 years old), the thesis includes a dimension of comparison with the general population of the same age group by taking into account the attitude scores of a sample of 601 students from other study programs. In accordance with the three specific objectives of the thesis, results show that, along the police training: 1) attitude scores of in-training police students more advanced in the curriculum are more positive and more divergent from those of the students from other study programs than these attitudes for freshmen, reflecting the impact of training in the development of the perceptions of police legitimacy in those on the path to serve as patrol officers, 2) attitude scores of the group of in-training police students more advanced in the curriculum are more homogenous than those of more novice groups of in-training police students, which suggests the adherence to a specific professional culture, and 3) in-training police students in the senior phase display a greater disconnection between their attitudes toward police legitimacy and attitudes toward police use of force compared to their more junior colleagues, in the sense that their attitudes towards police legitimacy are less strongly predictive of their attitudes toward police use of force. This last result sheds light on the development of critical judgment. All things considered, the thesis concludes that the worth of police initial training is far from vain; it strikes as being responsible for subtle and gradual attitude changes that can prove important to police work.

En collaboration avec Hydro-Québec à l'origine, notre laboratoire a développé un système de détection quantitative permettant de déterminer simultanément et en temps réel la concentration et le flux du C02 et du CH4. Les mesures de concentration sont effectuées par absorption infrarouge sur un parcours ouvert, jusqu'à environ 2000 mètres aller-retour, au-dessus de la surface émettrice au moyen de diodes lasers accordables. Les mesures sont effectuées à deux hauteurs séparées. Des concentrations de l'ordre d'une partie par million (ppm) pour le C02 et de 0,01 ppm pour le CH4 peuvent être mesurées selon la longueur du parcours et les conditions météorologiques. Les flux sont calculés à l'aide d'un modèle de diffusion simplifié qui utilise les données météorologiques provenant d'une station portable. Ce travail décrit le système d'origine et met l'emphase sur les transformations qui ont été réalisées dans le but d'optimiser son utilisation.

T follicular helper cells (T-FH) are a specialized subset of CD4 T cells that reside in B cell follicles and promote B cell maturation into plasma cells and long-lived memory B cells. During chronic infection prior to the development of AIDS, HIV-1 (HIV) replication is largely concentrated in T-FH. Paradoxically, T-FH numbers are increased in early and midstages of disease, thereby promoting HIV replication and disease progression. Despite increased T-FH numbers, numerous defects in humoral immunity are detected in HIV-infected individuals, including dysregulation of B cell maturation, impaired somatic hypermutation, and low quality of antibody production despite hypergammaglobulinemia. Clinically, these defects are manifested by increased vulnerability to bacterial infections and impaired vaccine responses, neither of which is fully reversed by antiretroviral therapy (ART). Deficits in T-FH function, including reduced HIV-specific IL-21 production and low levels of co-stimulatory receptor expression, have been linked to these immune impairments. Impairments in T-FH likely contribute as well to the ability of HIV to persist and evade humoral immunity, particularly the inability to develop broadly neutralizing antibodies. In addition to direct infection of T-FH, other mechanisms that have been linked to T-FH deficits in HIV infection include upregulation of PD-L1 on germinal center B cells and augmented follicular regulatory T cell responses. Challenges to development of strategies to enhance T-FH function in HIV infection include lack of an established phenotype for memory T-FH as well as limited understanding of the relationship between peripheral T-FH and lymphoid tissue T-FH. Interventions to augment T-FH function in HIV-infected individuals could enhance immune reconstitution during ART and potentially augment cure strategies.